Feel free to ask questions. I'll do my best to answer.

Thursday, December 23, 2010

I'm going to try and summarize some basic psychoacoustic phenomenon important for the audio, speaker, home recording or home theater enthusiast. It's hard for me to determine what is important to start with so I guess I'll start with explaining myself a bit. My understanding and writing of this is in no way comprehensive and it's not intended to be so. I just want to make this stuff accessible to those who don't want to read giant books.

So briefly: 1) The Haas Effect, often referred to as the precedence effect, is the principle that the first arriving sound tells the ear where the sound is coming from. Your head takes all those reflections inside roughly 30 milliseconds and integrates them into the original. Even if the delayed sound is up to 10 dB louder, the ear will still integrate it into the original. Reflections after this time period are heard as echoes and within this time period they contribute to the timbre, add spaciousness and a sense of detail to the recorded material.

That brings me to my next point, 2) a loudspeaker's polar response. If all those early reflections are integrated into the original, shouldn't they be spectrally similar to the original? Sound waves are coming off a loudspeaker in all directions, bouncing off your walls and into your listening space. It certainly seems reasonable for sound reproduction. This may sound like I'm advocating an omnidirectional speaker, but it's not so simple. I would think in the right room and positioning, I'd bet that Mr. Linkwitz's Pluto would be an outstanding speaker. Anyone in the Bay area has one and would let me listen, Just write me! :D

OK, I'll move onto just one more quick point today. I personally want to hear what's on the recording--not some radical distortion of it that may sound good to me on certain songs or whatever and terrible on others, so a flat frequency response is pretty much a must and a smooth off axis set of responses has to be there as well due to Mr. Haas's discovery. If the recording is really bad, your going to need an EQ--you'll need one anyway as I'll discuss later beneath 300 Hz.

5 comments:

Thanks for your information on this excellent blog. I came across your blog while I am doing some information search on Haas effect. I have a digital speaker setup that allows me to experiment on various settings

http://www.digitalroomcorrection.hk/Site/Welcome.html

I have just setup my surround speaker with the signal from 60Hz to 2000Hz delayed by 10ms. I found that the soundstage is richer and wider, with better timber and only a slight loss in focussing. I am still experimenting on different delay and loudness of the surround speakers. But your description sums it up very well!

Thanks for your very kind comments. Regarding the issue on polar pattern, there is a recent AES paper on Horbach and Keele crossover filter. There are 2 white papers on Linkwitzlab site which are very interesting

Siegfred Linkwitz lives in the bay area, Marin County, he has invited me a few times to come over to his home and listen to what he is currently doing, but I never took him up on it. I probably should as he has really aged in the last four years (the last time I saw him) I just saw him last month. He is still very enthusiastic about audio and I alway have excellent conversations with him. This last time he was going on about all the advantages of the slot loaded woofer array of Nelson Pass' speakers that he was listening to at Burning Amp. I just listened. The slot loaded woofers are an OB type speaker, but the front is slot loaded so increases the efficiency and lower the effective fs. Both very useful with an OB woofer array.

Last time I saw SL, I was so star struck I could barely speak! It was pathetic. That man is a living audio encyclopedia. If he remembers me, he probably thinks I'm a moron. lol. I was sweating, my voice was shaky, and my heart was racing. I just walked away quickly. :( Seemed like a nice guy though.